China's tea culture has a long history, and tea is one of China's major symbols. China is the origin of tea trees. Tea trees first appeared in the Yunnan-Guizhou plateau and Xishuangbanna area in the southwest of China. According to inspections, the word “Tea” first appeared in the “Hundred Masters Monument” and “Wui Fai Monument”, and it was about the middle of the Tang Dynasty, from about 806 AD to around 820 AD; later, the Tea Sutra was also adopted. The word "tea". Prior to this, "tea" was represented by "荼". There are hundreds of modern Chinese teas. According to its historical analysis, there are three kinds of situations: the restoration of historical teas and traditional teas, most of which belong to newly established teas.

Xiao Bian remembers that when he was young, the men in his hometown liked to hold cups and have a cup of tea in hand, which made him feel very comfortable. The demand for tea in our country is very large, because it is well-known that drinking tea has many benefits, so the place for growing tea is also increasing.

The techniques used to produce tea include picking, drying, spreading, seeing green, shaking green, killing green, kneading, and baking. In the process of fixing (greening) the purpose is to use high temperatures, quickly destroy the activity of the enzyme, and consolidate the already formed quality. How is the temperature specific?

The killing process first requires the rapid and timely destruction of the enzyme's catalysis. Temperature is one of the most important factors affecting the catalytic action of enzymes. Within a certain temperature range, the temperature rises, which not only speeds up the catalytic reaction of the enzyme, but also accelerates the destruction of the enzyme. The optimum temperature for so-called enzymatic action is that at this temperature (under certain conditions) the maximum amount of enzymatic reactant is reached.

At the optimum temperature, the rate of catalysis of the enzyme doubles for every 10°C increase in temperature. The optimum temperature of general plant enzymes is 50-60°C. Some data suggest that the optimum temperature of polyphenol oxidase in tea leaves is 52°C.

As the temperature rises, the enzyme also deteriorates due to thermal effects. When the temperature exceeds the optimal temperature of the enzyme, the enzyme activation is lost. The former is larger than the latter due to an increase in activation caused by an increase in temperature, resulting in a decrease in the speed of the enzymatic reaction. The higher the temperature, the greater the drop. When the temperature rises to a certain limit, the enzyme is completely destroyed and the enzymatic reaction rate is zero. This temperature limit is called the critical temperature of enzyme passivation.

In the process of fixing, high temperature must be used to quickly increase the temperature of the fixing leaves in an extremely short period of time, and quickly pass the optimum temperature of the enzyme to reach the critical temperature of enzyme passivation. The enzyme is completely destroyed by heat and it is difficult to determine how high the temperature is. Because of the other factors. In the process of fixing, the critical temperature of passivation of polyphenol oxidase was determined. According to the data measured by Anhui Agricultural College, it was initially assumed to be 85°C. The critical temperature of enzyme passivation in tea needs to be further studied. However, according to some test results, the fixing process requires that the temperature of the leaf quickly rises above 85°C.

The time required for the leaf temperature to rise from room temperature above 85°C is one of the most important factors in the fixation technique. From the above, it can be seen that the enzymatic reaction is quite dramatic before the temperature of the leaf rises above the critical temperature for the passivation of the enzyme. If the period of warming up is prolonged and the amount of change is relatively increased, chemical changes in the contents of the leaf may be transferred to the “deteriorated” route, resulting in the generation of red stems and red leaves. The general fixation technology requires that leaf temperature rises above 85°C within a period of two minutes, and the maximum time should not exceed three or four minutes. Otherwise, red stems and red leaves may appear. Leaf temperature above 85°C will continue for a certain period of time. After the complete destruction of the enzymes, the temperature of the leaves should be reduced. Especially when the water content of the leaf is reduced to nearly 60%, the leaf temperature is too high, and the individual shoots and tips of the high tenderness will be coked.

Tea not only requires temperature during production, but also has strict requirements on temperature during storage. Tea moisture absorption and strong odor absorption, it is easy to absorb moisture and odor in the air, if the storage method is a little improper, it will lose flavor in a short period of time, and the more the Qing Dynasty fermentation of high-quality aromatic tea, the more difficult to save. Usually after the tea is stored for a period of time, the aroma, taste and color will change, the original new tea will disappear, and the taste of the tea will be gradually exposed. Temperature: Storage of tea leaves at higher temperatures will accelerate the aging of new teas and change the quality of tea. Generally, the temperature of the tea leaves is increased by 3 to 5 times for every 10°C increase in temperature. If tea leaves can be stored below 0°C, aging can be almost completely prevented. The temperature recorder can come in handy at this time, LCD can display the recorded temperature, grasp the temperature, and store the tea.

Modified Starch

On the basis of the inherent characteristics of natural starch, in order to improve the properties of starch and expand its application range, physical, chemical or enzymatic treatment is used to introduce new functional groups on starch molecules or change the size of starch molecules and the properties of starch granules. Thereby changing the natural characteristics of starch (such as: gelatinization temperature, thermal viscosity and its stability, freeze-thaw stability, gel strength, film-forming, transparency, etc.), making it more suitable for certain application requirements. This starch that has undergone secondary processing and changed its properties is collectively referred to as modified starch.

As one of the important raw and auxiliary materials in industry, modified starch can be widely used in papermaking, food, textile, construction, medicine and other industries. The production enterprises shall actively develop new products and expand the application fields of modified starch.

1. Denatured starch for food should be functional, diverse and convenient. New varieties should be developed in grain processing, focusing on the development of corn series products and potato starch, modified starch and derivative products; We will develop convenience food, nutrition and health food, and emulsifying thickening quality improvers. Therefore, modified starch for food can be developed into functional modified starch, modified starch for convenience food and alkenyl succinate starch which is in short supply in China. As a food additive, denatured starch should take into account the increasing trend of hypertension and hyperlipidemia patients in China, develop fat substitutes and sugar substitutes that have energy and nutritional value and do not affect blood sugar, so as to meet the needs of increasing incidence rate of diabetes patients year by year. At present, fat substitutes based on starch can be used in almost all foods that need to add fat; The developed anti digestible starch has low water holding capacity, fine particles, fresh flavor, and the microcrystalline structure is smaller than that of ordinary dietary fiber. It can also be used as a functional component in a variety of foods.

2. The development speed of denatured starch that is 100% substituted for chemical size PVA also needs to be accelerated. The modified starch used for textile sizing is mainly acid hydrolyzed starch, oxidized starch, urea starch, phosphate starch, and a small amount of acetate starch and compound modified starch. These varieties are difficult to replace the chemical size PVA, especially in the sizing of high branch yarn products. Due to its non degradability, PVA is gradually used or even not used in textile sizing materials. Similar products have been put on the market abroad. It is believed that with the efforts of people in the domestic denatured starch industry, this product can be fully developed.

3. The development of new surface coating agents and sizing in the paper industry is beneficial to meet the needs of the product structure of the national paper industry. Denatured starch is an important papermaking chemical. The amount of denatured starch used in papermaking in China is 1 / 3 of the total amount of denatured starch in the country, but the variety is single and the level is low. At present, the product structure of the national paper industry is to develop towards high-grade newsprint, book printing paper, information paper, office paper and other medium and high-grade domestic paper, which requires the development of new surface coating agents and sizing agents to meet the needs of the paper industry.

4. Starch based water absorbent is widely used. Water absorbent can be used in agriculture, forestry, horticulture, medicine and health, textile, papermaking, oil drilling, construction, wastewater treatment and food processing. At present, some industries rely on a large number of imported expensive water absorbent products to meet the market demand, and most of the imported products are polymer synthetic products. With the depletion of oil and increasing attention to environmental protection, the market of this kind of products is facing a crisis. The development direction of this product is to use renewable natural starch resources to undergo graft copolymerization with acrylic acid or acrylonitrile through chemical treatment, and connect hydrophilic macromolecules on the starch to prepare biodegradable water absorbent to replace the water absorbent re synthesized by petroleum refining.

In a word, with the growth of China's economy, the continuous expansion of the scale of industrial products, the continuous development of the application field of modified starch, the continuous development of new products and the continuous innovation of new processes, the demand for modified starch will also increase; In addition, with the gradual reduction of natural oil, the modified starch produced from renewable resources is a substitute for many petrochemical products, which brings development space for modified starch. Therefore, the development prospect of modified starch will be very broad.

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